I really wish there would be a widget (talking about the computer side) that would allow to control the phone's media player the same way it can be done over bluetooth (AVRCP). It would be good to not need bluetooth to be enabled just to control the media player and also it should control the device's volume (the multimedia part).
Beside that, there could be a streaming option to play sound from computer on the device (makes sense when it is connected to speakers). I know there are already android apps that do it, but having it on AirDroid along with all these other features would be better. But I don't consider this as something important. The control of the music player is much more useful.